Joey,
As above, everyone has great ideas, in the end, if your looking into making it a BOL. You'd better have a consistent community of preppers that are willing to defend it. I agree with Dannyboy, any determined force will find a way in and do a number on you. Just ask Bin-Ladin, if a determined force has something worth venturing inside, no door or wall is going to stop them. If you do plan to develop it, I'd make sure you have some exfil and rally points for your preppers and have a second BOL to hang your hat. In fact, if you do opt to do that, I'd say, don't place all your eggs in one basket, located many cache sites along your exfil route and not store it all in your castle. Not sure what your population density is for that area, but from your first picture, it sits astride a ridgeline. First thing you learn as a basic infantryman, is to stay off the ridge. That first group of pictures with the tall keep is like some person waving a flag to come on over. Not wanting to play Debbie Downer (oh, sorry American Saturday Night Live phrase), AKA not trying to sound negative, but its going to be like a chick magnet for a very desperate person who is in need of food, etc...remember, your talking roving bands of people...like your ancestors had to deal with in the 1200's and your going to have to prepare for a siege, but if they have access to heavy stuff like RPGs, c-4, or even a working mortar,...ask 11C1P, he was one and I no doubt could with a good crew, he could make that castle into rubble in a couple of hours.
I like the idea of fixing it up into bedrooms. Real world, you have a money maker there for tourists. You could advertise it on a vacation home website. Heck, I'd come there for a vacation, just make sure you have a few more blankets, my wife's toes get cold at night. So here is a crazy thought, fix it up, rent the rooms like a bed and breakfast, hire some good actors dressed in period, and use the money to build up your preps. You could use the lower half of your castle as a storage site and develop another off-site BOL. Just some off thoughts, but it might work, without you having to sell the family heirloom off to some greedy speculator. Be ware of the Chinese, they own us, through Walmart!
Again, really a nice dig, wish we all inherited something like that here in America, but then Big government gets our stuff anyway. Rich get richer, poor well they just keep applying to Big Government.
Regards